Located either within endometrium or in the direct sub-endometrial tissue

They are small calcifications or crystals

are they dangerous?

No. These are almost invariably due to previous "event" of some sort in the uterus, most often, instrumentation.

Spontaneous or Therapeutic Abortion

Dilatation and Curretage

C-Section

Sexually Transmitted Disease.

dictation macro

"There are scattered endometrial (or subendometrial) calcifications likely due to previous instrumention." (This is my standard dictation macro. However, it would be fine to include the other potential etiologic factors described above.

The important thing is to NOT raise alarm as this is an innocuous finding.